This project will provide timely and rigorous analysis of the effect of the Affordable Care Act's (ACA) insurance coverage expansions on health care use and outcomes among a large cohort of low-income adults in 12 southern states (VA, WV, KY, TN, NC, SC, FL ,GA, AL, MS, LA, AR). The ACA's coverage reforms encompass the largest insurance expansion since Medicare and Medicaid in 1965. Examining the effects of expansions on health care and outcomes for socio-demographic and clinical groups intended to benefit from expanded coverage will be critical to advancing scientific knowledge about the relationship between insurance coverage and health and to informing state decisions to expand Medicaid over the next several years. In no region of the country are rates of uninsurance higher, the prevalence of chronic conditions and cancer greater, and the implementation of the ACA's coverage expansions expected to be more varied, than in the South. The proposed 5-year research project will draw on these regional characteristics and the largest cohort of low- income, uninsured, and minority adults ever recruited in the US (nearly 85,000 in total), the Southern Community Cohort Study (SCCS). We will augment existing baseline and follow-up SCCS survey data from 2002-2014 by fielding a timely additional survey in the second year of ACA reforms (2015) and by adding questions to a planned round of follow-up in 2016-2017 to support consistent assessment of early and later effects of the reforms on health and to explore patient experiences obtaining coverage and accessing care in the post-expansions era. By combining these data with cancer registry and Medicare and Medicaid claims data through established data linkages, as well as establishing novel data linkages with state hospital discharge databases, we aim to quantify the effects of coverage expansion on: (Aim 1) access to care, cancer screening and use of preventive clinical services; (Aim 2) self-reported health outcomes, mortality and use of emergent and inpatient care; and (Aim 3) cancer stage at diagnosis and quality of cancer care for adults with breast, lung, and colorectal cancer. We will groups likely to be uninsured before coverage reforms as well as adults with prior coverage whose access to care could plausibly be compromised by coverage expansions for others. To identify these effects, we will apply rigorous quasi-experimental difference-in-difference designs, exploiting both within- and between-state variation in coverage expansions. Our analytic approach will also incorporate regression and propensity score-based adjustment to balance observed characteristics between comparison groups. Finally, due to the longitudinal nature of our data and high observed mortality rates in the cohort, where appropriate we will use advanced methodological approaches to modeling death and health outcomes jointly. In short, our timely quasi-experimental analyses will help characterize the value of the ACA's coverage reforms, will inform policy debates over coverage expansions moving forward, and will advance understanding of the effects of insurance coverage on health care use and health outcomes.